A dam around the Water Fountain Nebula? The dust shell of IRAS16342-3814 spatially resolved with VISIR/VLT

Abstract

Either by collimating a fast stellar wind or by driving a jet via accretion in the central system, dusty torii or stable disks may be crucial ingredients for the shaping of PNe. We study the dust distribution in the very young Proto-Planetary Nebule (PPN) IRAS16342-3814, also known as the Water Fountain Nebula, which is known to show strong bipolar characteristics in the shape of two reflection lobes, and high-velocity collimated molecular outlfows. We use the new Mid-IR (MIR) instrument VISIR on the Very Large Telescope (VLT) both in imaging and spectroscopy mode at wavelengths from 8 to 13 micron. We present the first spatially resolved MIR observations of a dusty evolved star obtained with VISIR and find that the improved spatial resolution contradicts previous claims of an elliptical brightness distribution at the heart of IRAS16342: we find the waist region to be dark even in the MIR. We show that the filling angle of the obscuring dust lane, which is made mostly of amorphous silicates, is very large, possibly even close to a spherically symmetric superwind as seen in OH/IR stars. We conclude that, in contrast to the multitude of recent dusty-disk detections in Post-AGB stars and PNe, IRAS16342 does not show this extreme equatorial density enhancement, at least not on the scale of the dusty environment which lends the object its IR appearance. Rather, it appears that the observed precessing jets are shaping the bipolar nature in the remains of a spherically symmetric AGB superwind.

5 pages, accepted for publication in A&A

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Cited by in corpus (13)

• A mid-infrared imaging catalogue of post-AGB stars
• The optically bright post-AGB population of the LMC
• ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-velocity bipolar jets and an Expanding Torus
• Establishing a mass-loss rate relation for red supergiants in the Large Magellanic Cloud
• Herschel/PACS observations of the 69 $\mu m$ band of crystalline olivine around evolved stars
• The problematically short superwind of OH/IR stars - Probing the outflow with the 69 μm spectral band of forsterite
• HD101584: Circumstellar characteristics and evolutionary status
• CO J=3-2 Emission from the "Water Fountain" Sources IRAS 16342-3814 and IRAS 18286-0959
• Extremely Strong ^{13}CO J=3-2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning
• Do Water Fountain Jets Really Indicate the Onset of the Morphological Metamorphosis of Circumstellar Envelopes?
• Dust shell model of the water fountain source IRAS 16342--3814
• A Fast bipolar H2 outflow from IRAS 16342-3814: an old star reliving its youth
• CRIRES-VLT high-resolution spectro-astrometry as a tool in the search of small structures at the cores of Planetary Nebulae